Camera with an exposure control function

ABSTRACT

A camera according to this invention includes a backlight judgment section which determines whether the photographic scene is against light by comparing the average luminance of the entire photographic screen obtained by photometry with the luminance of the main subject at a distance-measuring point selected by distance measurement. With the backlight judgment section, the camera performs suitable exposure control accompanied by illumination, such as supplementary light, at the time of exposure in a photographic scene where the main subject is against light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2002-268732, filed Sep. 13,2002; No. 2002-271816, filed Sep. 18, 2002; and No. 2002-321314, filedNov. 5, 2002, the entire contents of all of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a camera which performs correct exposurecontrol by determining whether the subject is against light at the timeof measuring the brightness of the subject, and also to a technique ofprocessing image data in cameras.

2. Description of the Related Art

In a scene where the main subject is photographed against light orbacklit as when there is a light source, such as the sun, behind themain subject, the shady part of the main subject is photographed, withthe result that the main subject collapses in black.

To prevent this, the shady part of the main subject is lighted by thereflected light from a reflecting plate or illuminating light.Alternatively, when a picture is taken, strobe light is caused to emitlight, that is, daylight synchronized flash is done.

In making a decision on backlighting, if the area occupied by the mainsubject is large for the photographic screen, it is easy to make adecision. However, in a photographic scene where the area occupied bythe main subject is small, the luminance difference becomes smaller,which can cause a case where it cannot be determined that the subject isagainst light. To overcome this problem, for example, Jpn. Pat. No.2934712 has disclosed an exposure control method of additionallyproviding a focal point detecting section (distance measuring section)to the photometric section for measuring the brightness in the middle ofand the periphery of the photographic screen.

In the invention of Jpn. Pat. No. 2934712, the backlit state of the mainsubject is detected with a distance-measuring sensor. For example, in aphotographic scene as shown in FIG. 3, the distance measuring sensorsets only region 33 b as the distance measuring range in the area of thephotographic screen 34T.

Furthermore, concerning a method of preventing improper exposure in abacklit photographic scene, a related technique has been disclosed in,for example, Jpn. Pat. Appln. KOKOKU Publication No. 7-27151. In thismethod, a camera capable of measuring the brightness and distance in aplurality of areas on the photographic screen selects one of the areason the basis of the distance-measuring data. The photometric value inthe selected area is compared with the maximum one of the photometricdata in the other areas, thereby making a decision on backlighting. Whenit is determined that the photographic scene at that time is againstlight, daylight synchronized flash has been done.

Moreover, in a digital camera, when a backlit scene is not subjected toa suitable image process, the resulting image is unnatural andunattractive. For instance, the contour of the main subject deforms dueto the spread of light, which makes it difficult to reproduce a naturalimage.

To overcome this problem, for example, Jpn. Pat. Appln. KOKAIPublication No. 8-107519 or Jpn. Pat. Appln. KOKAI Publication No.11-32236 has disclosed the technique for analyzing the luminancedistribution of the image data obtained by the imaging element by use ofa histogram or the like to detect backlighting and changing the imageprocessing method. Those techniques are for balancing the brightness ofthe main subject with the brightness of the background, making use ofthe photographed images.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided acamera comprising: a sensor array which detects an image signal of asubject existing in a specific position on a photographic screen and hasa plurality of sensors; a computing section which calculates the averagevalue of the outputs of a part of the plurality of sensors in the sensorarray; an average photometric sensor which detects the averagebrightness at the photographic screen; an average luminance computingsection which calculates the average luminance value at the photographicscreen on the basis of the output of the average photometric sensor; anda subject state judgment section which determines the state of thesubject by comparing the average value of the sensor outputs with theaverage luminance value and a judgment section which determines exposurecontrol during photographing on the basis of the average luminance valueand the results of the determinations at the subject state judgmentsection.

According to another aspect of the present invention, there is provideda camera comprising: a sensor array which detects an image signal of asubject existing in a specific position on a photographic screen and hasa plurality of sensors; a computing section which calculates the averagevalue of the outputs of a part of the plurality of sensors in the sensorarray; an average photometric sensor which detects the averagebrightness of visible light at the photographic screen; an averageluminance computing section which calculates the average luminance valueat the photographic screen on the basis of the output of the averagephotometric sensor; an infrared photometric sensor which detects aninfrared luminance value indicating the brightness of the averageinfrared light at the photographic screen; a subject state judgmentsection which determines the state of the subject by comparing theaverage value of the sensor outputs with the average luminance value; asubject field state judgment section which determines the state of asubject field including the subject by comparing the average luminancevalue with the infrared luminance value; and an exposure controldetermining section which determines exposure control duringphotographing on the basis of the average luminance value and theresults of the determinations at the subject state judgment section andthe subject field state judgment section.

According to still another aspect of the present invention, there isprovided a camera comprising: a photometric section which measures thesubject luminance in a plurality of areas on a photographic screen; adistance-measuring section which measures the subject distance in aplurality of areas on the photographic screen; a first select sectionwhich selects one from a plurality of distance-measuring areas on thephotographic screen on the basis of the distance-measuring data abouteach distance-measuring area; a second select section which selects onefrom the photometric area corresponding to the distance-measuring areaselected by the first select section and its adjacent photometric areason the basis of the photometric data about each photometric area; and abacklight judgment section which makes a decision on backlighting bycomparing the photometric data about the photometric area selected bythe second select section with the photometric data about eachphotometric area.

According to still another aspect of the present invention, there isprovided a camera comprising: an imaging section which detects a subjectimage signal; a backlighting state judgment section which determineswhether the subject is against light; a strobe unit which emits strobelight onto the subject on the basis of the result of the decision onbacklighting at the backlighting state judgment section; and an imageprocessing section which compares the brightness of the subject withthat of the background when the strobe unit emits the strobe light ontothe subject, changes the amount of correction by a gamma conversionprocess or a contour emphasizing process on the basis of the result ofthe comparison, and processes the image of the subject image signaldetected by the imaging section.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 shows a schematic configuration of the exposure control system ofa camera related to a first to a third embodiment of the presentinvention;

FIG. 2 shows a concrete configuration provided on the camera of thefirst embodiment;

FIG. 3 shows the relationship between the photographing area and thedistance-measuring area on the photographic screen;

FIGS. 4A, 4B, 4C, and 4D show the arrangement of distance-measuringpoints (areas) and light-receiving example of obtained image data;

FIG. 5 is a flowchart to help explain exposure control in the firstembodiment;

FIGS. 6A and 6B are flowcharts to help explain a first modification ofthe first embodiment;

FIGS. 7A and 7B are flowcharts to help explain a second modification ofthe first embodiment;

FIG. 8 is a diagram to help explain the relationship between the visiblelight luminance and the infrared high luminance in the firstmodification;

FIG. 9 shows a concrete configuration provided on the camera of thesecond embodiment;

FIGS. 10A, 10B, 10C, and 10D show an outward appearance and a part ofthe inside of the camera in the second embodiment;

FIG. 11 is a flowchart to help explain exposure control in the secondembodiment;

FIG. 12 is a diagram to help explain the relationship between the pixelarea of the imaging element and the distance-measuring area (point) ofthe AF sensor;

FIGS. 13A and 13B show concrete configurations provided on the camera ofthe third embodiment;

FIG. 14 is a block diagram of the main part of a camera with aphotometric function according to a fourth to a seventh embodiment ofthe present invention;

FIG. 15 schematically shows a configuration of the photometric sectionrelated to the fourth to sixth embodiments;

FIG. 16 schematically shows a configuration of the distance-measuringsection related to the fourth to sixth embodiments;

FIG. 17 shows the relationship between the photometric area and thedistance-measuring area in the fourth embodiment;

FIG. 18 shows the relationship between the photometric area and thedistance-measuring area in the fifth embodiment;

FIG. 19 is a flowchart to help explain the release sequence of a cameraprovided with the photometric device related to the fourth to sixthembodiments;

FIG. 20 is a flowchart to help explain a decision on backlighting in thefourth embodiment;

FIG. 21 is a flowchart to help explain a decision on backlighting in thefifth embodiment;

FIG. 22 is a flowchart to help explain a decision on backlighting in thesixth embodiment;

FIG. 23 schematically shows a configuration of the photometric anddistance-measuring section in the seventh embodiment;

FIG. 24 is a block diagram of a camera according to an eighth embodimentof the present invention;

FIG. 25 is a diagram to help explain the sensor array and the monitoringrange of the imaging section;

FIG. 26A shows an example of a backlit scene, FIG. 26B is a distributiondiagram of brightness in the photographic scene of FIG. 26A, FIG. 26Cshows an example of the photographic scene after strobe light is emittedonto the photographic scene of FIG. 26A, FIG. 26D is a distributiondiagram of brightness in the scene of FIG. 26C, FIG. 26E shows aphotographic scene when strobe light has not reached the subject, andFIG. 26F is a distribution diagram of brightness in the photographicscene of FIG. 26E;

FIG. 27A is a histogram of brightness when the γ value is normal, FIG.27B is a histogram of brightness when the γ value is made smaller, FIG.27C is a histogram of brightness after the emission of strobe light, andFIG. 27D is a histogram of brightness when the γ value is made largerwhen strobe light has not reached the subject;

FIG. 28 is a distribution diagram of brightness when the photographicscene is not against light;

FIG. 29 is an explanatory diagram about a γ conversion process;

FIG. 30A shows a functional configuration of the contour emphasizingsection and FIG. 30B is a diagram to help explain contour emphasizingcalculation;

FIGS. 31A and 31B are flowcharts to help explain the sequence ofphotographing control of the camera related to the eighth embodiment;

FIG. 32 is a diagram to help explain the assimilation of a person's hairand the background in the γ conversion process;

FIG. 33 is a flowchart to help explain the sequence of photographingcontrol of a camera related to a ninth embodiment of the presentinvention;

FIG. 34A is a positional distribution diagram of the amount ofintegration outputted from the imaging section before the emission ofstrobe light, FIG. 34B is a positional distribution diagram of theamount of integration outputted from the imaging section when sufficientstrobe light has not been emitted onto the main subject, and FIG. 34C isa positional distribution diagram of the amount of integration outputtedfrom the imaging section when sufficient strobe light has been emittedonto the main subject;

FIG. 35 is a flowchart to help explain the control sequence of backlightphotographing with a camera related to a tenth embodiment of the presentinvention;

FIG. 36A shows a change in the amount of integration with respect totime of the background subject after the emission of strobe light andFIG. 36B shows a change in the amount of integration with respect totime of the main subject when sufficient strobe light has been emittedonto the main subject after the emission of strobe light;

FIG. 37A shows a change in the amount of integration with respect totime of the background subject after the emission of strobe light andFIG. 37B shows a change in the amount of integration with respect totime of the main subject when sufficient strobe light has not beenemitted onto the main subject after the emission of strobe light; and

FIG. 38A is a positional distribution diagram of brightness when thebrightness difference between the person and the background is small,FIG. 38B is a diagram to help explain the γ conversion process in FIG.38A, FIG. 38C is a positional distribution diagram of brightness whenthe brightness difference between the person and the background islarge, and FIG. 38D is a diagram to help explain the γ conversionprocess in FIG. 38C.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, referring to the accompanying drawings, embodiments of thepresent invention will be explained.

The basic idea of making a decision on backlighting with the exposurecontrol system of a camera related to the first embodiment of thepresent invention will be explained by reference to FIG. 1.

The exposure control system includes the component parts explainedbelow.

The exposure control system includes a photometric sensor (AE sensor) 1for determining the luminance (photometric value) in visible light onthe entire photographic screen, an average luminance computing section 2for determining the average luminance of the entire screen from theobtained photometric value, a distance-measuring sensor 3 for performinga distance-measuring operation on a plurality of distance-measuringpoints on the photographic screen, and a distance computing section 4for determining the distance to the subject from the distance-measuringdata obtained in the distance-measuring operation. The exposure controlsystem further includes a subject select section 5 for setting, forexample, the one existing at the closest distance as the main subjectfrom the results of measuring the distance and selecting the position ofthe main subject as a distance-measuring point (hereinafter, referred toas a point) on the photographic screen. The exposure control systemfurther includes a luminance computing section 6 for computing thequantity (luminance) of light entering the selected point, a backlightjudgment section 7 for determining the state of the subject from theluminance of the selected point and the average luminance, a strobelight emission section 8 for emitting supplementary light duringbacklighting, an infrared photometric sensor 52 for receiving by remotecontrol and determining the luminance of infrared light of the entirephotographic screen, an artificial light judgment section 53 fordetermining the state of the field including the luminance of theinfrared light and the average luminance, a mode discriminative section56 for discriminating the present photographic mode set by a mode changesection 55 explained later, and a control section 9 for determiningexposure control in photography including strobe light emission control.

The light-receiving face of the photometric sensor 1 is separated into aperipheral photometric section la and the central photometric section 1b. In the embodiment, the backlight judgment section 7 serving assubject state decision means determines whether the subject is againstlight or backlit. The artificial light judgment section 53 serving assubject field state decision means determines whether the light sourceof the subject field is artificial.

The exposure control system further includes a photometric backlightjudgment section 10 for making a decision on backlighting by comparingthe individual outputs of the divided photometric sensor sections. Thedecision on backlighting is effective when the main subject exists inthe middle of the photographic scene. The artificial light judgmentsection 53, which determines whether the light source is of naturallight or artificial light (for example, incandescent lamp light orfluorescent lamp light), compares the output of the infrared photometricsensor 52 with the output of the average luminance computing section 2.When the subject 27 exists under artificial light, the artificial lightjudgment section 53 serves to prevent color seepage by artificial light(for example, green seepage under fluorescent lamp light).

When the exposure control system is actually constructed of the averageluminance computing section 2, distance computing section 4, subjectselect section 5, luminance computing section 6, backlight judgmentsection 7, control section 9, photometric backlight judgment section 10,and artificial light judgment section 53, the control and computingprocesses are realized by a single microcomputer (CPU).

In the exposure control system, the exposure operation is started by theturning on of the release switch or the like of the camera (not shown).First, the photometric sensor 1 and infrared photometric sensor 52measure brightness. From the resulting photometric values, the averageluminance computing section 2 determines the average luminance ofvisible light and the luminance of infrared light on the entire screen.

Next, the distance-measuring sensor 3 measures the distance to each ofthe points on the photographic screen one after another. Using theresulting distance-measuring data, the distance computing section 4determines the distance to the subject at each point. The subject selectsection 5 determines the closest one of the subject distances at theindividual points to be the point where the main subject is present andselects the point as a point to be focused on. The luminance computingsection 6 monitors and finds the luminance of the selected point.

Next, the backlight judgment section 7 compares the average luminance ofthe entire screen with the luminance of the selected point, therebydetermining whether the photographic scene is against light. If theaverage luminance of the entire screen is higher than the luminance ofthe selected point, the backlight judgment section 7 determines that thesurroundings are brighter than the main subject, that is, the mainsubject is against light. Furthermore, the artificial light judgmentsection 53 compares the luminance of infrared light on the entire screenwith the luminance of visible light at the average luminance computingsection 2, thereby determining whether the subject is in artificiallight. To photograph a scene against light and a scene illuminated withartificial light, strobe light is emitted according to the ISOsensitivity of the photographing medium (such as the imaging element orfilm), the aperture value, and the distance to the subject. In this way,a decision on backlighting is made on the basis of the brightness of theselected point (the position of the main subject) and the brightness ofthe entire screen and color seepage by artificial light is prevented,which enables proper exposure control. When the average luminance islower than the luminance of the point, it is determined that the mainsubject is not against light, with the result that exposure control isperformed suitably without emitting strobe light.

FIG. 2 shows a concrete configuration of the electronic circuit systemof a camera as a first embodiment to which the exposure control systemof the present invention is applied. The camera of the first embodimentis a digital camera that converts the subject image into image data witha photoelectric conversion element, carries out various image processes,and records the resulting data.

The camera is roughly composed of a photometric distance-measuringsystem, an image pickup optical system, and an imaging system. Acalculation control section (CPU) 11, which controls the entire camera,is composed of a one-chip microcomputer or the like.

The photometric distance-measuring system includes a distance-measuringsection 25 for measuring the distance to a subject 27, an A/D conversionsection 14 for A/D converting the subject image signal from thedistance-measuring section 25 and outputting a digital image signal,split-type sensors 16 a, 16 b for receiving the light gathered by an AElens 15, and an AE circuit 17 which is composed of a logarithmiccompression circuit and others and measures the brightness of the insideof the photographic screen. The distance-measuring section 25 iscomposed primarily of two light-receiving lenses 12 a, 12 b provided thebase length B away from each other, and a pair of sensor arrays 13 a, 13b for receiving the subject image formed by the lenses 12 a, 12 b andgenerating a subject image signal by photoelectric conversion.

The image pickup optical system is composed of a photographic lens (zoomlens) 18 for forming an image of the subject, a lens driving mechanism(LD) 19 for driving the photographic lens 18 to bring the camera intofocus, and a zoom driving mechanism 24 for changing the angle ofcoverage by moving the lens barrel. The imaging system includes animaging element (CCD) 20 for creating image data on the basis of theimage of the subject formed by the photographic lens 18, an imageprocessing section 21 for subjecting the image data obtained from theimaging element 20 to image processes, including γ conversion and imagecompression, and a recording section 22 for recording the image datasubjected to image processing.

The imaging system further includes a switch input section (releaseswitch) 23 for starting a specific sequence in the calculation controlsection 11 in response to the operation of the photographer, a strobeemitting section 26 for emitting supplementary illumination light ontothe subject 27, a strobe driving section 28 for performing drivingcontrol of the strobe emitting section 26, an infrared photometriccircuit 54 for receiving the signal from an infrared remote control anddetecting the infrared light component from the subject 27, and a modechanging section 55 for selectively setting the desired one of, forexample, the aperture-value priority mode, shutter-speed priority mode,strobe forced-emission mode, strobe OFF mode, spot photometric mode, andinfinite mode.

As for the component parts of the camera, only the members related tothe subject matter of the first embodiment of the present invention aredescribed. Explanation of the other component parts an ordinary camerahas, such as the finder, will be omitted, because they are supposed tobe included.

The two light-receiving lenses 12 a, 12 b provided the base length Bapart gather light, which is then converted photoelectrically by a pairof sensor arrays 13 a, 13 b and further A/D converted by A/D conversionsection 14. The A/D conversion section 14 produces a pair of digitalimage signals from a pair of analog signals produced by the pair ofsensor arrays 13 a, 13 b. The CPU 11 compares the digital signals,thereby determining the relative positional difference x between theimage input positions.

Since the subject distance L, the focal length f of the light-receivinglens, and the base length B vary in such a manner that they fulfill theequation x=B·f/L as shown in FIG. 2, detecting x enables the focusingdistance L to be calculated. Since the sensor arrays are extendedhorizontally, when a photographic scene as shown in FIG. 3 is aimed at,the area 33 a is monitored. The area 33 a is divided into seven blocksas shown in FIG. 4A and the aforementioned detection is carried outusing the image signal of each block, which enables the distance ofseven points on the screen to be measured. Of the seven results ofmeasurements, for example, the closest distance is determined to be themain subject distance.

When the photographic lens 18 is a zoom lens, the angle of view isturned to the telephoto side, which enables only the photographic area34T on the screen in the photographic scene shown in FIG. 3 to bephotographed. At this time, if the distance-measuring area continues tobe area 33 a, things outside the screen are also measured in distance.Therefore, in the telephoto mode, the distance-measuring area isnarrowed to area 33 b. As shown in FIG. 4B, multipoint AF (multi-AF) ofseven points in the seven narrowed areas is carried out. The AE circuit17 and sensor arrays 16 a, 16 b measure the brightness of visible lighton the entire screen. On the basis of the result of the measurement, theCPU 11 performs exposure control. In the sensor arrays 16 a, 16 b, theoutput of the sensor array 16 a, or the area (in the telephoto mode) 32shown in FIG. 3, is selected in the telephoto mode according to a changein the angle of view caused by the zooming of the photographic lens. Inthe wide angle mode, the sum of the outputs of the sensor arrays 16 a,16 b, or the area (in the wide angle mode) 31 is selected and photometryis performed. Furthermore, the infrared photometric sensor 52 andinfrared photometric circuit 54 measure the luminous intensity ofinfrared light on the entire screen (photometric range 52R).

Each of the septsected distance-measuring points shown in FIGS. 4A and4B is composed of rectangular pixels arranged in a plurality of columns.Since each pixel outputs data according to the shade of the image, imagedata as shown in FIG. 4D is obtained. By averaging the image data fromthe individual pixels, the average luminance of each point isdetermined. Use of multi-AF enables the position of the main subject tobe detected and further the luminance at the position to be determined,which makes it possible to photograph by exposure control putting stresson the main subject, according to a flowchart shown in FIG. 5.

An example of using the photometric sensors and distance-measuringsensors of the first embodiment will be explained by reference to aflowchart in FIG. 5.

First, the zoom position of the photographic lens 18 is determined (stepS1). From the determined zoom position, it is determined whether thephotographic lens 18 has been turned to the wide angle side (step S2).In this determination, if the lens 18 has been turned to the wide angleside (YES), the angle of view 34W is set as shown in FIG. 3 and thephotometric range 31 and distance-measuring range 33 a are selected(step S3). On the other hand, if the photographic lens 18 has beenturned to the telephoto side, not to the wide angle side (NO), the angleof view 34T is set and the photometric range 32 and distance-measuringrange 33 b are selected (step S4).

Distance measuring is done in the distance-measuring range selected asdescribed above (step S5). Of the results of the measurements, the point(distance-measuring point) indicating the closest distance where themain subject exists is set as the selected point (step S6). The mainsubject average photometric value SP_(AVE) indicating the brightness ofthe image output at the selected point is calculated (step S7). Then,the AE sensor selected in step S4 measures the luminous intensity in thephotometric range (photographic screen) (step S8) and calculates theaverage photometric value BV_(AVE), the average of the outputs obtainedin the photometry (step S9).

On the basis of the main subject distance obtained in step S6, the ISOsensitivity of photographing mediums (including the imaging element andfilm), and information on the zoom position-obtained in step S1, theguide number of the strobe unit is calculated and it is determinedwhether strobe light reaches the main subject (step S10). If it has beendetermined that the strobe light reaches the main subject (YES), it isdetermined whether the average photometric value BV_(AVE) is equal to orlarger than a specific value BV_(O) (step S11). That is, the reliabilityof the obtained main subject average photometric value SP_(AVE) isdetermined on the basis of the average photometric value. Since theoutput of the distance-measuring sensor does not pass through thelogarithmic compression circuit, the linearity of photometry (dynamicrange) is limited. In step S11, it is determined whether the averagephotometric value BV_(AVE) is equal to or larger than the specific valueBV_(O).

In step S11, if the average photometric value BV_(AVE) is larger thanthe specific value BV_(O) (YES), the main subject average photometricvalue SP_(AVE) is considered reliable. The main subject averagephotometric value SP_(AVE) is compared with the average photometricvalue BV_(AVE), thereby determining whether the average photometricvalue BV_(AVE) is larger than the value SP_(AVE), that is, whether thesubject is against light (step S12).

On the other hand, if it has been determined in step S10 that strobelight does not reach the main subject (NO), if it has been determined instep S11 that the average photometric value BV_(AVE) is smaller than thespecific value BV_(O) (NO), or if it has been determined in step S12that the average photometric value BV_(AVE) is smaller than the mainsubject average photometric value SP_(AVE) (NO), exposure control isperformed on the basis of the average photometric value BV_(AVE), takingno account of the main subject average photometric value SP_(AVE) (stepS13). Then, the sequence is completed.

On the other hand, if it has been determined in step S12 that theaverage photometric value BV_(AVE) is larger than the main subjectaverage photometric value SP_(AVE) (YES), or if it has been determinedthat the photographic scene is against light with the surroundingsbrighter than the main subject, or that the photographic scene needs theemission of strobe light, exposure is made with strobe light serving assupplementary light (step S14). Then, the sequence is completed.

As described above, with the first embodiment, the point for bringingthe subject into focus on the photographic scene is caused to coincidewith the point for exposure adjustment and a decision on backlighting ismade by comparing the photometric values (luminances). Thus, thephotographer has only to press the release button to make a decision onbacklighting and make exposure suitable for the photographic scene. As aresult, the photographer can take a picture in focus with a goodexposure.

Since whether strobe light reaches the main subject properly is takeninto account, it is possible to prevent the battery from being consumeddue to a useless emission of strobe light.

As a first modification of the first embodiment which realizes exposurecontrol putting stress on the main subject, an example of usingphotometric sensors, distance-measuring sensors, and infraredphotometric sensors will be explained by reference to a flowchart shownin FIG. 6. Because step S21 to step S27 in the first modification arethe same as step S1 to step S7 in the aforementioned flowchart, theywill be explained briefly.

First, the zoom position of the photographic lens 18 is determined. Fromthe zoom position, it is determined whether the photographic lens 18 ison the wide angle side. If the photographic lens 18 has been turned tothe wide angle side, the angle of view 34W is set as shown in FIG. 3 andthe photometric range 31 and distance-measuring range 33 a are selected.On the other hand, if the lens 18 has not been turned to the wide angleside, the angle of view 34T is set and the photometric range 32 anddistance-measuring range 33 b are selected (step S21 to step S24).Distance measuring is done in these selected distance-measuring ranges.Of the results of the measurements, the point (distance-measuring point)indicating the closest distance where the main subject exists is set asthe selected point. The main subject average photometric value SP_(AVE)indicating the brightness of the image output at the selected point iscalculated (step S25 to step S27).

Then, the photometric sensor (AE sensor) 1 selected in steps S23, S24measures the luminous intensity of visible light in the photometricrange and the infrared photometric sensor 52 measures the luminousintensity of infrared light (step S28). Then, the average photometricvalue BV_(AVE), the average of the outputs obtained at the photometricsensor 1, is calculated (step S29). In addition, the infraredphotometric value BVr obtained at the infrared photometric sensor 52 iscalculated (step S30).

Then, it is determined whether the camera photographic mode set by themode changing section 55 is the strobe OFF mode to inhibit the emissionof strobe light, the infinite mode to photograph the subject in thedistance, or the spot photometric mode to measure the luminous intensityonly in the central part of the screen (step S31). In thisdetermination, if any one of the modes has been set (YES), controlproceeds to step S37 explained later. On the other hand, if none of themodes has been set (NO), the guide number of the strobe unit iscalculated on the basis of the main subject distance, the ISOsensitivity of photographing mediums (including the imaging element andfilm), and information on the zoom position obtained in step S21. Then,it is determined whether strobe light reaches the main subject (stepS32).

In step S32, if it has been determined that strobe light does not reachthe main subject (NO), control goes to step S37 explained later. On theother hand, if it has been determined in step S32 that strobe lightreaches the main subject (YES), it is determined whether artificiallight has been detected, on the basis of the average photometric valueBV_(AVE) of visible light and the infrared photometric value BVr (stepS33).

As shown in the relationship between the visible light luminance and theinfrared light luminance (wide ISO 100) of FIG. 8, if BV_(AVE)<visiblelight luminance Lv13 and BV_(AVE)>BVr+3.5 (Lv), it is determined thatlight is emitted from a fluorescent lamp, whereas if BV_(AVE)<Lv13 andBV_(AVE)<BVr, it is determined that light is emitted from anincandescent lamp. If such artificial light has been detected (YES),control proceeds to step S38 explained later, where exposure accompaniedby the emission of strobe light is made. On the other hand, ifartificial light has not been detected (NO), it is determined that thereis no color seepage. Then, it is determined whether the subject has alow luminance in visible light (step S34). This determination is made,using BV_(AVE)<Lv 10 as a decision criterion as show in FIG. 8. In thedetermination, if the subject has a low luminance (YES), control goes tostep S38. If the subject has not a low luminance (NO), it is determinedwhether the average photometric value BV_(AVE) is equal to or largerthan a specific value BV_(O) (step S35). A decision on the reliabilityof the obtained main subject average photometric value SP_(AVE) is madeon the basis of the average photometric value. Specifically, since theoutput of the distance-measuring sensor does not pass through thelogarithmic compression circuit, the linearity (dynamic range) ofphotometry is limited. Thus, in step S35, it is determined whether theaverage photometric value BV_(AVE) is equal to or larger than thespecific value BV_(O).

In step S35, if it has been determined that the average Photometricvalue BV_(AVE) is larger than the specific value BV_(O) (YES), the mainsubject average photometric value SP_(AVE) is considered reliable. Themain subject average photometric value SP_(AVE) is compared with theaverage photometric value BV_(AVE), thereby determining whether theaverage photometric value BV_(AVE) is larger than the value SP_(AVE),that is, whether the subject is against light (step S36).

If it has been determined in step S31 that the photographic mode is anyone of the strobe OFF mode, infinite mode, and spot photometric mode(YES), if it has been determined in step S32 that strobe light does notreach the main subject (NO), if it has been determined in step S35 thatthe average photometric value BV_(AVE) is smaller than the specificvalue BV_(O) (NO), or if it has been determined in step S36 that theaverage photometric value BV_(AVE) is smaller than the main subjectaverage photometric value SP_(AVE) (NO), exposure control is performedon the basis of the average photometric value BV_(AVE), taking noaccount of the main subject average photometric value SP_(AVE) (stepS37). Then, the sequence is completed.

On the other hand, if it has been determined in step S33 that artificiallight has been detected (YES), it has been determined in step S34 thatthe main subject has a low luminance (YES), or if it has been determinedin step S36 that the average photometric value BV_(AVE) is larger thanthe main subject average photometric value SP_(AVE) (YES), that is, ithas been determined that the photographic scene is against light withthe surroundings brighter than the main subject, or that thephotographic scene needs the emission of strobe light, exposure is madewith strobe light serving as supplementary light (step S38). Then, thesequence is completed.

As described above, the first modification not only produces the sameeffect of the first embodiment but also prevents the occurrence of colorseepage because of the emission of strobe light taking color seepageinto account on the basis of a decision on artificial light. This makesit easier to take a picture of a natural shade in proper focus withadjusted exposure.

Furthermore, a second modification of the first embodiment will beexplained by reference to a flowchart shown in FIG. 7. The secondmodification is such that the sequence of the distance-measuring stepand the photometric step in the first modification is reversed and thestep of determining whether strobe light reaches the subject is omitted.In the second modification, the same steps as those in the firstmodification are indicated by the same reference numerals and will beexplained briefly. Step S39 to step S41 in the second modificationcorrespond to step S28 to step S30 in the first modification. Step S42to S44 in the second modification correspond to step S25 to step S27 inthe first modification.

First, the zoom position of the photographic lens 18 is determined. Fromthe zoom position, it is determined whether the photographic lens 18 ison the wide angle side. If the photographic lens 18 has been turned tothe wide angle side, the angle of view 34W is set as shown in FIG. 3 andthe photometric range 31 and distance-measuring range 33 a are selected.On the other hand, if the lens 18 has not been turned to the wide angleside, the angle of view 34T is set and the photometric range 32 anddistance-measuring range 33 b are selected (step S21 to step S24).

Then, the photometric sensor (AE sensor) 1 selected in steps S23, S24measures the luminous intensity of visible light in the photometricrange and the infrared photometric sensor 52 measures the luminousintensity of infrared light. Then, the average photometric valueBV_(AVE), the average of the outputs obtained at the photometric sensor1, is calculated. In addition, the infrared photometric value BVrobtained at the infrared photometric sensor 52 is calculated (step S39to step S41).

Then, distance measuring is done in the selected distance-measuringrange 33 a or 33 b. Of the results of the measurements, the point(distance-measuring point) indicating the closest distance where themain subject exists is set as the selected point. The main subjectaverage photometric value SP_(AVE) indicating the brightness of theimage output at the selected point is calculated (step S42 to step S44).

If it has been determined in step S31 that any one of the strobe OFFmode, infinite mode, and spot photometry mode has been set (YES), if ithas been determined in step S32 that strobe light does not reach themain subject (NO), if it has been determined in step S35 that theaverage photometric value BV_(AVE) is smaller than the specific valueBV_(O) (NO), or if it has been determined in step S36 that the averagephotometric value BV_(AVE) is smaller than the main subject averagephotometric value SP_(AVE) (NO), meaning that the subject is not againstlight, exposure control is performed on the basis of the averagephotometric value BV_(AVE), taking no account of the main subjectaverage photometric value SP_(AVE) (step S37). Then, the sequence iscompleted.

On the other hand, if it has been determined in step S33 that artificiallight has been detected (YES), it has been determined in step S34 thatthe main subject has a low luminance (YES), or if it has been determinedin step S36 that the average photometric value BV_(AVE) is larger thanthe main subject-average photometric value SP_(AVE) (YES), that is, ithas been determined that the photographic scene is against light withthe surroundings brighter than the main subject, or that thephotographic scene needs the emission of strobe light, exposure is madewith strobe light serving as supplementary light (step S38). Then, thesequence is completed.

In the second modification, the distance can be measured, taking intoaccount the results of measurements by the photometric sensors.Therefore, it is possible to take a picture in accurate focus withproper exposure without being influenced by the luminance.

A second embodiment of the present invention will be explained.

FIG. 9 shows a conceptual configuration of a camera related to thesecond embodiment. In the second embodiment, the like component parts asthose of FIG. 2 are indicated by the same reference numerals andexplanation of them will be omitted. While the distance-measuringsection 25 of the first embodiment requires a pair of light-receivinglenses 12 a, 12 b and a pair of sensor arrays 13 a, 13 c, adistance-measuring section 40 of the second embodiment uses alight-receiving lens 41, a sensor array (external array sensor) 42, aphotographic lens 18, and an imaging element 20 to make trigonometricdistance measurements.

Trigonometric distance measurements are made as follows. Thephotographic lens 18 is set in a specific position. It is determined inwhich part of the sensor array 42 the same image as the image dataobtained in the central part of the screen of the CCD 20 can bedetected. From the result of the determination, the subject distance Lis found on the principle of trigonometric distance measurements. Ofcourse, use of the image data in the part deviating from the centralpart of the screen enables the distance of the main subject not existingin the middle of the screen to be measured as shown in FIG. 3. In thiscase, the sensor array 42 is composed of a plurality of columns ofsensor arrays as shown in FIG. 10B. FIG. 10A shows an outward appearanceof and a part of the inside of a camera 51 provided with thedistance-measuring section of the second embodiment.

In the camera 51, the photographic lens 18 is provided almost in thecenter of the camera front. Above the photographic lens 18, thelight-receiving lens 41 and strobe emitting section 26 are provided sideby side. On the top of the camera, the release switch 23 is provided.Inside the camera, the imaging element 20 is provided behind thephotographic lens 18 and the sensor array 42 is provided behind thelight-receiving lens 41.

The sensor array 42 is composed of, for example, three line sensorsarranged side by side as shown in FIG. 10B to measure the distance ofthe main subject shifted laterally from the center of the photographicscreen. A lateral arrangement of sensor arrays 42 with respect to thephotographic screen 50 as shown in FIG. 10C makes it possible to monitorthe main subject moved sideways (42L) or standing aside as shown in FIG.10D.

Accordingly, with the second embodiment, a space corresponding to onelight-receiving lens and the cost of one sensor array can be saved. Thelight-receiving lens and the photographic lens can be provided with awider space between them, with the result that the base length B becomeslonger and therefore higher accuracy can be realized.

Referring to a flowchart shown in FIG. 11, exposure control in thecamera of the second embodiment will be explained.

First, information on the zoom position of the photographic lens 18 isdetermined. On the basis of the information about the zoom position, thefocus position of the photographic lens 18 is set to a specific position(step S51). The position setting makes the relationship between thephotographic lens 18 and the imaging element 20 almost equal to therelationship between the light-receiving lens 41 and the sensor array42. This is done to increase the distance-measuring accuracy by makingthe focus position of the photographic lens 18 almost equal to that ofthe light-receiving lens 41. In the setting, one pixel of the sensorarray 42 does not correspond to one pixel of the imaging element 20 in aone-to-one ratio. To overcome this problem, all of the outputs of tenpixels, 2×5, of the imaging element 20 are added and caused tocorrespond to one pixel of distance-measuring image data (step S52). Theaddition matches the distance-measuring range (output) of the sensorarray 42 with that of the imaging element 20.

Next, multi-AF is performed by trigonometric distance measurements (stepS53). From the obtained distance-measuring data, the position of themain subject is detected (the point is selected) (step S54). Then,focusing is done so as to meet the position of the main subject or thedistance to the selected point (step S55). During the focusing, theoutput of the imaging element 20 is monitored and a fine adjustment ofthe position of the photographic lens 18 is made so that the contrast ofthe image formed on the light-receiving surface of the imaging element20 may be optimum.

Next, the exposure value is determined from the output of all of theimaging element 20 (step S56). Next, using the AF sensor, thedistance-measuring value of only the position of the main subject iscalculated (step S57). For example, in a photographic scene as shown inFIG. 10D, the average value of the output of the sensor array 42Lmonitoring the existence of the main subject is found as thedistance-measuring value.

Next, on the basis of the main subject distance obtained in step S54,the ISO sensitivity of photographing mediums (including the imagingelement and film), and information on the zoom position obtained in stepS51, the guide number of the strobe unit is calculated. Then, it isdetermined whether strobe light reaches the main subject (step S58).

If it has been determined that strobe light reaches the main subject(YES), the average photometric value of the entire screen by the imagingelement 20 is compared with the photometric value by the sensor array 42of the area where the main subject can possibly exist, therebydetermining whether the subject is against light (step S59). If theaverage photometric value of the entire screen is larger than thephotometric value of the main subject (YES), it is determined that thephotographic scene is against light. Then, exposure accompanied by theemission of strobe light is made (step S60), which completes thesequence.

If it has been determined in step S58 that the strobe light does notreach the main subject (NO), or if it has been determined in step S59that the photometric value of the main subject is larger than theaverage photometric value of the entire screen (NO), normal exposure ismade on the basis of the photometric value of the main subject (stepS61), which completes the sequence.

Consequently, with the second embodiment, a space corresponding to onelight-receiving lens and the cost of one sensor array (external light AFsensor) can be saved. The light-receiving lens and the photographic lenscan be provided with a wider space between them, with the result thatthe base length B becomes longer and therefore higher accuracy can berealized. In photometry by the AF sensor, one sensor 61 can representten pixels of data of the imaging elements 62 a to 62 j, which enablesthe average value to be calculated easily at a high speed. Sinceconsideration is given to whether strobe light reaches the main subjectproperly, it is possible to prevent the battery from being consumed dueto a useless emission of strobe light.

Next, a third embodiment of the present invention will be explained.

FIG. 13A shows an outward appearance of the camera viewed from thefront. FIG. 13B shows an internal configuration with the exterior of thecamera removed.

In the first and second modifications, the photometric sensors,distance-measuring sensors, and infrared photometric sensors have beenused. When they are mounted on the camera, various limits are set totheir locations, because the camera is required to be more compact andlighter. That is, the individual parts have to be mounted collectivelyso as not to allow a useless space, while assuring the performance ofthe camera.

The camera 71 is in the photographing standby state, with the frontcover 71 opened and the lens barrel 76 of the photographic lensprotruded. Above the lens barrel 76, the finder 72 and thedistance-measuring sensor 3 are provided side by side. At the top rightof the front, the strobe-emitting section 26 is provided. Thephotometric sensor 1 is provided below the finder 72 and in the vicinityof the lens barrel 76 and distance-measuring sensor 3.

On both sides between which the lens barrel 76 is sandwiched, a Patronecompartment 73 for loading a detachable film cartridge (not shown) and aspool compartment 74 provided with a spool (not shown) for winding thefilm. On the underside of the camera body, there is provided a winder 75that is coupled with the film cartridge and spool and feeds the film.The film feeding includes winding and rewinding the film.

Below the finder 72 and in the place enclosed by the lens barrel 76 andPatrone compartment 73, the remote control sensor, or the infraredphotometric sensor 52, is provided.

The photometric sensor 1 and infrared photometric sensor 52 are providedin the space left after the primary component parts, including the lensbarrel 76, Patrone compartment 73, and winder 75, are incorporated,which eliminates a useless space and therefore contributes to theminiaturization of the camera. The present invention is not limited tothe arrangement of the photometric sensors and distance-measuringsensors. They have only to be provided in the vicinity of the finder.This arrangement helps reduce the parallax with respect to the finderduring photometry and distance measurement.

The less the parallax of each of the photometric sensor 1,distance-measuring sensor 3, and infrared photometric sensor 52 withrespect to the finder is, the more accurately the distance measurementand photometry of the subject desired by the user are performed.Although it is desirable that the photometric sensor 1,distance-measuring sensor 3, and infrared photometric sensor 52 shouldbe provided as close to the finder as possible, it is difficult toprovide a plurality of component elements in a specific place of thecamera from the viewpoint of the miniaturization of the camera. Sincethe infrared photometric sensor 52 has only to detect the infrared lightluminance of the whole subject field, there is no problem even when theparallax of the infrared photometric sensor 52 with respect to thefinder is greater than that of the photometric sensor 1 ordistance-measuring sensor 3. Therefore, in the third embodiment, theinfrared photometric sensor 42 is provided farther away from the finderthan the photometric sensor 1 and distance-measuring sensor 3, therebyrealizing not only accurate photometry and distance measurement but alsothe miniaturization of the camera.

As described above, with the first to third embodiments, even in aphotographic scene where a decision on backlighting was difficult tomake in the prior art, proper exposure is made with a simple operationby comparing the photometric value of the area where the main subjectexists with the photometric value of the entire photographic screen,making a decision on the backlighting state correctly to determinewhether to emit strobe light, and making a decision on artificial lightto determine whether to emit strobe light. Therefore, it is possible toprovide an camera enabling the user to enjoy photography.

With the exposure control system of the embodiments of the presentinvention, it is possible to provide a camera capable of making adecision on backlighting by comparing the luminance of the area wherethe main subject exists in the photographic screen with the averageluminance of the photographic screen and photographing the main subjectwith proper exposure without being influenced by the composition of thephotographic scene. Furthermore, the camera, which is provided with theartificial light judgment section, compares visible light with infraredlight. When light illuminating the subject is artificial, for example,fluorescent lamp light, the camera can photograph the subject withproper exposure so as to prevent color seepage, such as the greening ofthe image.

Next, a fourth to a seventh embodiments of a camera with a exposurecontrol function according to the present invention will be explained.

FIG. 14 shows an example of the basic configuration of a camera with aphotometric function according to the fourth embodiment of the presentinvention. The basic configuration is assumed to be equivalent to thebasic configuration of cameras related to not only the fourth embodimentbut also the fifth to seventh embodiments explained later.

A camera 80 includes a photometric section 81 for measuring informationon the luminance of the subject in the photographic scene and adistance-measuring section 82 for measuring information on the subjectdistance on the same photographic scene. The camera 80 further includesa lens driving section 83 for driving a focusing-lens on the basis ofthe obtained distance-measuring information, a shutter section 84 forexposing the film, a film feeding section 85 for winding and rewindingthe film, and a strobe unit 86 for emitting light and illuminating thesubject when the subject is low in luminance or against light.

The camera 80 further includes a nonvolatile memory, such as EEPROM 87,for storing various setting values and adjusting values for the camera80 and a CPU 88 for controlling the operation sequence of the wholecamera 80 and doing calculations.

The camera 80 further includes a 2-stage release switch composed of afirst release switch (hereinafter, abbreviated as “1RSW”) 89 and asecond release switch (hereinafter, abbreviated as “2RSW”) 90. 1RSW89 isused for the photographer to inform the camera of the measuring ofinformation on the subject necessary for photography, such as distancemeasurements or photometry and the execution of calculations. 2RSW90 isused to inform the camera of the execution of photography on the basisof the measured and calculated subject information, after 1RSW89 hasbeen turned on.

The CPU 88 performs control of all of the camera according to a releasesequence program (often called a camera sequence program) serving as avirtual control program. In the control program, the following sectionsare constructed in software: for example, they are a first selectsection 91 for selecting the distance-measuring area whosedistance-measuring data indicates the closest distance from a pluralityof distance-measuring areas on the photographic screen, a second selectsection 92 for selecting the photometric area corresponding to thedistance-measuring area whose distance-measuring data indicates theclosest distance selected by the first select section and thephotometric area whose photometric data indicates the lowest luminancefrom its adjacent photometric areas, and a backlight judgment section 93for making a decision on backlighting on the basis of the differencebetween the photometric data about the photometric area with the lowestluminance selected by the second select section and the averagephotometric data on the photographic screen.

The distance-measuring section 81 and photometric section 82 mounted onthe camera 80 are configured as shown in FIGS. 15 and 16.

FIG. 15 schematically shows an example of the configuration of thephotometric section 81 related to the fourth to sixth embodiments. Thephotometric section 81 includes a photometric lens 101 for gatheringlight components at the photographic screen for photometricmeasurements, a multidivisional photometric sensor 102 for dividing thegathered light components into a plurality of regions and receivingthem, a photometric integration control section 103 for controlling theintegrating operation of the multidivisional photometric sensor 102, andan A/D conversion section 104 for converting the integration output ofthe multidivisional photometric sensor 102 from the analog signal into adigital signal, with the A/D conversion section 104 connected to themultidivisional photometric sensor 102. With this configuration, thedigital signal produced by a known photometric method to calculate thebrightness of the subject is supplied to the CPU 88.

FIG. 16 schematically shows the configuration of the distance-measuringsection 82 related to the fourth to sixth embodiments. Thedistance-measuring section 82 includes a pair of light-receiving lenses105 a, 105 b for forming the image of the subject for distancemeasurement, a pair of line sensors 106 a, 106 b for photoelectricallyconverting the subject image formed by the light-receiving lenses 105 a,105 b according to their light intensity to produce an electric signal(subject image signal), a distance-measuring (AF) integration controlsection 107 for controlling the integrating operation of the linesensors 106 a, 106 b, and an A/D conversion section 108 for reading thesubject image signal from the line sensors 106 a, 106 b and convertingthe analog signal into a digital signal. With this configuration, thedigital signal which is produced by a known distance-measuring methodand used for calculating the distance to the subject is supplied to theCPU 88.

To help understand the characteristics of the fourth embodiment, thesubject image in distance measurement and photometry and the area wherethe image can be detected will be explained.

FIG. 17 schematically shows the relationship between the photometricarea and the distance-measuring area in the fourth embodiment. In theareas for photometry and distance measurement, an image of a person 109,the main subject to be photographed, is emitted as shown in the figure.The areas for photometry and distance measurement are divided in amatrix on the finder screen (or image forming screen), which forms thefollowing types of areas.

In the fourth embodiment, the photometric section 81 measures theluminous intensity in each of the photometric areas divided into a largenumber of rectangles as shown by solid lines in FIG. 17. Thedistance-measuring section 82 measures the distance to each of therectangular distance-measuring areas arranged in the middle in thelongitudinal direction as shown by broken lines.

From the distance-measuring areas, the one whose measured distance isthe closest is selected. The photometric area corresponding to theselected distance-measuring area is selected. Thereafter, from theselected photometric area and the adjacent photometric areas on bothsides, the one whose photometric result is the lowest luminance isselected.

For example, when the distance-measuring area 110 presentsdistance-measuring data about the closest distance, an adjacentphotometric area 111 and an adjacent photometric area 113 are present onboth sides of the photometric area 112 corresponding to thedistance-measuring area 110.

Here, an algorithm related to the processes up to a decision onbacklighting will be explained.

For example, when the distance-measuring data about thedistance-measuring area 110 in FIG. 17 indicates the closest distance,the photometric area 112 is selected. It is assumed that the photometricdata items about the photometric area 112 and its adjacent photometricareas 111, 113 are B_(VAE) 112, B_(VAE) 111, and B_(VAE) 113,respectively, and their relationship in luminance level meets theexpression B_(VAE) 113<B_(VAE) 112<B_(VAE) 111. In this case, thephotometric data B_(VAE) 113 about the photometric area 113 whosephotometric data indicates the lowest luminance is selected.

Next, the average photometric data B_(VAE)AVE of the individualphotometric areas is determined. When the difference between the averagephotometric data B_(VAE)AVE and the photometric data B_(VAE) 113selected as described above is larger than a backlight decision valueGBvTH as a threshold value, it is determined that the subject is againstlight.

Specifically, with backlight decision value GBvTH=2EV, if the followingexpression is met:B _(VAE) AVE−B _(VAE) 113>2  (1)it is determined that the photographic scene is against light.

If it is determined that the photographic scene is against light, thephotometric data B_(VAE) 113 about the photometric area 113 is set asphotometric data used in exposure calculations. On the other hand, if itis determined that the photographic scene is not against light, theaverage photometric data B_(VAE)AVE about the photographic screen is setas photometric data used in exposure calculations.

The reason why the photometric data about the lowest luminance isselected from the photometric area corresponding to the closestdistance-measuring area and its adjacent photometric areas is that, whenthe closest distance-measuring area 110 includes both of the image of aperson 109, the main subject, and the background in the visual field asshown in FIG. 17, the photometric data B_(VAE) 112 about the photometricarea 112 corresponding to the distance-measuring area 110 has theaverage of the luminance of the image of a person 109 against light withthe high luminance background, with the result that it can possibly bedetermined that the photographic scene is not against light, even if thescene is actually against light.

As a modification of the fourth embodiment, the largest photometric datain a plurality of photometric areas on the photographic screen may beused in place of the average photometric data B_(VAE)AVE on thephotographic screen, when a decision on backlighting is made. Thisprevents the photographic scene from being determined erroneously to benot against light in a case where the low luminance part occupies alarge proportion of the background of the main subject and the mainsubject itself is against light. Thus, it is possible to prevent theexposure of the main subject from being improper due to the misjudgment.

Furthermore, when a decision on backlighting is made, exposure controlmay be performed with the emission of light from the strobe unit,instead of exposure control based on the lowest photometric data. Inthis exposure control, the main subject is exposed properly with strobelight and the background is exposed properly for the exposure time.

While the line sensors have been used in the distance-measuring section82, an area sensor may be used to make two-dimensional distancemeasurements. Use of the area sensor enables a decision on backlightingto be made in a much wider area on the photographic screen.

Next, the operation and control of the camera related to the fourthembodiment will be explained in detail. FIG. 19 shows a flowchart forthe release sequence of the camera provided with the photometric unitrelated to the fourth embodiment of the present invention. Thisflowchart serves as the main routine common to the fifth to seventhembodiments explained later.

First, when the power switch (not shown) of the camera is turned on,previously stored data, including various setting values and adjustingvalues, are read from the EEPROM 87 and expanded into a RAM (not shown)in the CPU 88. Then, initial setting is done (step S71).

Next, it is determined whether the power switch is in the OFF state(step S72). If the power switch is in the ON state (NO), it isdetermined whether 1RSW 89 is turned on (step S73). On the other hand,if the power switch is in the OFF state (YES), the sequence iscompleted.

If it has been determined in step S73 that 1RSW89 is in the ON state(YES), a specific photometry is performed and photometric data abouteach of the photometric areas on the photographic screen is calculated(step S74). On the other hand, if 1RSW89 is in the OFF state (NO),control returns to step S72 and is standing by.

Next, a specific distance measurement is made and distance-measuringdata about each of the distance-measuring areas on the photographicscreen is calculated (step S75). Thereafter, on the basis of the resultof the photometry obtained in step S74 and the result of the distancemeasurement in step S75, a decision on backlighting explained later ismade (step S76).

On the basis of the exposure computing data set in the decision onbacklighting in step S76, exposure calculations are done, therebydetermining exposure control data (step S77). On the basis of thecalculated subject distance data, the amount of protrusion of thefocusing lens (not shown) is calculated (step S78).

After the calculations are completed, it is determined whether 1RSW89 isin the ON state (step S79). If 1RSW89 is in the ON state (YES), it isdetermined whether 2RSW90 is in the ON state (step S80). On the otherhand, if 1RSW89 is not in the ON state (NO), control returns to stepS72.

If it has been determined in step S80 that 2RSW90 is in the ON state(YES), the lens driving section 83 protrudes the focusing lens accordingto the amount of lens protrusion determined in step S78 (step S81). Onthe other hand, if 2RSW90 is not in the ON state (NO), control returnsto step S79.

Next, after the protrusion of the lens is completed, the shutter section84 makes exposure according to the exposure control data obtained instep S77 (step S82). Thereafter, the film feeding section 85 rolls upone frame of the film. Then, control returns to step S72 again.

Referring to a flowchart shown in FIG. 20, a characteristic subroutine“backlight decision” in the fourth embodiment will be explained.

First, the closest distance-measuring data is found from thedistance-measuring data about each of the distance-measuring areas onthe photographic screen measured in step S75 of FIG. 19. Then, thedistance-measuring area corresponding to the closest distance-measuringdata is selected (step S91). Next, the photometric area corresponding tothe selected distance-measuring area is selected (step S92). From theselected photometric area and its adjacent photometric areas, the lowestluminance photometric data is selected (step S93).

Next, from the photometric data about the individual photometric areasin step S74 of FIG. 19, the average photometric data (B_(VAE)AVE) on thephotographic screen is determined (step S94). Furthermore, thedifference between the lowest luminance photometric data selected instep S93 and the average photometric data found in step S94 iscalculated (step S95).

Then, the difference between the lowest luminance photometric data andthe average photometric data calculated in step S95 is compared with aspecific backlight decision value (threshold value: GBVTH=2EV) usingexpression (1) (step S96). In the comparison, if the difference in thephotometric data (B_(VAE)AVE−B_(VAE) 113) is larger than the backlightdecision value (2: in the fourth embodiment), it is determined that thephotographic scene is against light (YES) and the lowest luminancephotometric data selected in step S93 is set in the exposure computingdata (step S97). Thereafter, control returns to step S77 of FIG. 19. Onthe other hand, if the difference in the photometric data is not largerthan the backlight decision value (NO), it is determined that thephotographic scene is not against light and the average photometric dataB_(VAE)AVE on the photographic screen found in step S94 is set directlyin the exposure computing data (step S98). Thereafter, control returnsto step S77 of FIG. 19.

Next the fifth embodiment of the present invention will be explained.

The fifth embodiment is a photometric unit whose configuration isequivalent to that of the fourth embodiment, and so an explanation ofits configuration will be omitted.

To help understand the characteristics of the fifth embodiment, theimage of a subject in photometry and distance measurement and the areawhere the image can be detected will be explained.

FIG. 18 shows the relationship between the photometric area and thedistance-measuring area in the fifth embodiment. In the areas forphotometry and distance measurement, an image of a person 114, the mainsubject to be photographed, is emitted as shown in the figure. The areasfor photometry and distance measurement are divided in a matrix on thefinder screen (or image forming screen), which forms the following typesof areas.

For distance-measuring data about each distance-measuring area, forexample, there are a distance-measuring area 115 whosedistance-measuring data indicates the closest distance and adjacentdistance-measuring areas 116 and 117 on both sides of thedistance-measuring area 115.

Here, an algorithm related to the processes up to a backlight decisionwill be explained.

For example, of a plurality of rectangular areas arranged in the middlein the longitudinal direction shown by broken lines in FIG. 18, thedistance-measuring data about the distance-measuring area 115 indicatesthe closest distance, photometric data B_(VAF) 115, B_(VAF) 116, B_(VAF)117 are determined in the photometric area 115 and its adjacentphotometric areas 116, 117. If their level relationship in luminancelevel meets the expression B_(VAF) 117<B_(VAF) 115<B_(VAF) 116,photometric data B_(VAF) 117 about the distance-measuring area 117 whosephotometric data has the lowest luminance is selected.

Next, the average photometric data B_(VAE)AVE of the individualphotometric areas is determined. When the difference between the averagephotometric data B_(VAE)AVE and the photometric data B_(VAF) 117selected as described above is larger than a backlight decision valueGBvTH, it is determined that the photographic scene is against light.

Specifically, with the backlight decision value GBvTH=2EV, if thefollowing expression is met:B _(VAE) AVE−B _(VAF) 117>2   (2)

-   -   it is determined that the photographic scene is against light.

If it has been determined that the photographic scene is against light,the strobe unit 86 is caused to emit light during exposure. If it hasbeen determined that the photographic scene is not against light, theaverage photometric data B_(VAE)AVE on the photographic screen is set asphotometric data used in exposure calculations.

The operation and control in the fifth embodiment will be explained.

FIG. 21 is a flowchart for the sequence of a characteristic subroutine“backlight decision” in the fifth embodiment. FIG. 21 is a backlightdecision subroutine in step S76 of FIG. 19.

First, from the distance-measuring data about the distance-measuringareas on the photographic screen measured in step S75 of FIG. 19, theclosest distance-measuring data is found. The distance-measuring areacorresponding to the closet distance-measuring data is selected (stepS101). The photometric data about the selected distance-measuring areaand the photometric data about its adjacent distance-measuring areas arefound (step S102).

Next, from the photometric data found in step S102, the lowest luminancephotometric data is selected (S103). From the photometric data about thephotometric areas in step S74 of FIG. 19, the average photometric data(B_(VAE)AVE) on the photographic screen is calculated (step S104).

Next, the difference between the lowest luminance photometric dataselected in step S103 and the average photometric data found in stepS104 is calculated (step S105). The difference between the lowestluminance photometric data and the average photometric data calculatedin step S105 is compared with the backlight decision value (GBvTH=2EV)using the expression (2), thereby making a decision on which is largeror smaller (step S106).

If it has been determined that the difference in the photometric data islarger than the backlight decision value (2: in the fifth embodiment)(YES), it is determined that the photographic scene is against light. Todeal with the backlighting state, strobe light emission request settingis done by, for example, setting a strobe light emission request flag atthe strobe unit 86 (step S107). Thereafter, control returns to step S77of FIG. 19. On the other hand, if the difference in the photometric datais not larger than the backlight decision value (NO), it is determinedthat the photographic scene is not against light and the averagephotometric data on the photographic screen obtained in step S104 is setdirectly in the exposure computing data (step S108). Thereafter, controlreturns to step S77 of FIG. 19.

As described above, with the fifth embodiment, the luminance of the mainsubject in making a decision on backlighting is found using thedistance-measuring section 82, which not only produces a similar effectto that of the fourth embodiment but also can make a similar backlightdecision without using the multidivisional photometric element 102 (FIG.15) in the photometric section 81.

Next, the sixth embodiment of the present invention will be explained.

In the fourth and fifth embodiments, when it has been determined thatthe photographic scene is against light, the strobe unit 86 is caused toemit light during exposure. In actual photographing, however, there maybe a case where a sufficient effect cannot be obtained even whensupplementary light is supplied by the strobe unit 86, because ofvarious conditions, including the photographic lens with a large FNo.,the photographic scene with a long subject distance, and a low filmsensitivity. Since the configuration of the sixth embodiment isequivalent to that of the fourth embodiment, its detailed explanationwill be omitted.

In the sixth embodiment, when it is determined that the photographicscene is against light and supplementary light from the strobe unit 86cannot produce an acceptable effect, exposure control is performed onthe basis of the lowest luminance photometric data selected from thephotometric area corresponding to the closest distance-measuring areaand its adjacent photometric areas.

A decision on backlighting in the sixth embodiment will be explained byreference to a flowchart show in FIG. 22. FIG. 22 shows a subroutine fora decision on backlighting in step S76 of FIG. 19.

First, from the distance-measuring data about the distance-measuringareas on the photographic screen measured in step S75 of FIG. 19, theclosest distance-measuring data is found. Then, the distance-measuringarea indicating the value of the closest distance-measuring data isselected (step S111). The photometric area corresponding to the selecteddistance-measuring area is selected (step S112).

From the photometric area selected in step S112 and its adjacentphotometric areas, the lowest luminance photometric data is selected(step S113). From the photometric data about the individual photometricareas in step S74 of FIG. 19, the average photometric data on thephotographic screen is found (step S114). Furthermore, the differencebetween the lowest luminance photometric data selected in step S113 andthe average photometric data found in step S114 is calculated (stepS115).

Next, the difference between the lowest luminance photometric data andthe average photometric data calculated in step S115 is compared withthe backlight decision value (step S116). In the comparison, if thedifference in the photometric data is larger than the backlight decisionvalue (YES), it is determined that the photographic scene is againstlight. Furthermore, the effect of emitting supplementary light from thestrobe unit 86 in the backlighting state is estimated (step S117). Thatis, it is determined whether the closest distance-measuring data iswithin strobe light reaching distance is determined, taking into accountthe FNo. of the photographic lens and the film sensitivity. On the otherhand, if the comparison in step S116 has shown that the difference inthe photometric data is not larger than the backlight decision value(NO), it is determined that the photographic scene is not against lightand the average photometric data on the photographic scene found in stepS114 is set in the exposure computing data (step S120). Thereafter,control returns to step S77 of FIG. 19.

In step S117, if the closest distance-measuring data is within strobelight reaching distance (YES), it is determined that supplementary lightwill produce effects. Then, strobe light emission request setting isdone by setting a light emission request flag in the strobe unit 86(step S118). Thereafter, control returns to step S77 of FIG. 19. On theother hand, if the closest distance-measuring data is not within strobelight reaching distance (NO), the lowest luminance photometric dataselected in step S113 is set in the exposure computing data (step S119).Thereafter, control returns to step S77 of FIG. 19.

As described above, with the sixth embodiment, since it is determinedwhether the value of the obtained closest distance-measuring data iswithin strobe light reaching, taking into account the FNo. of thephotographic lens and the film sensitivity, the effect of strobe lightcan be estimated. Therefore, even when the emission of light from thestrobe unit 86 doesn't seem to have any effect in the backlightingscene, the main subject can be photographed with as proper exposure aspossible by setting the lowest luminance photometric data in theexposure computing data.

Next, the seventh embodiment of the present invention will be explained.

FIG. 23 schematically shows the configuration of a photometric sectionand a distance-measuring section in the seventh embodiment. The seventhembodiment is characterized by using a pair of area sensors 122 a, 122 bas shown in FIG. 23 in place of the distance-measuring section 82.Photometry is performed using one of the area sensors 122 a, 122 b.

A photometric distance-measuring section 125 in the seventh embodimentmeasures subject luminance data and subject image data. The photometricdistance-measuring section 125, which has the functions of thephotometric section 81 and distance-measuring 82, is an integralphotometric distance-measuring unit sharing a sensor function. Thephotometric distance-measuring section 125 is composed of a set oflight-receiving lenses 121 a, 121 b, area sensors 122 a, 122 b, anintegration control section 123, and an A/D conversion section 124.

Of these, the light-receiving lenses 121 a, 121 b form a subject imageon the light-receiving surface of the area sensors 122 a, 122 b. Thearea sensors 122 a, 122 b photoelectrically convert the subject imageformed on the light-receiving surface and produce an electric signal(photometric data or subject image signal) according to the lightintensity. The integration control section 123 performs control relatedto the integrating operation of the area sensors 122 a, 122 b. The A/Dconversion section 124 reads the photometric data or subject imagesignal produced by the area sensors 122 a, 122 b and converts the dataor analog signal into a digital signal.

That is, in place of the line sensors (106 a, 106 b) used in thedistance-measuring section 82, the area sensors 122 a, 122 b are usedfor distance measurements. At least one of the area sensors is used forphotometry.

With this configuration, distance measurement and photometry areperformed as described above. The processing sequence of distancemeasurement and photometry conform to that in the aforementionedembodiments and its detailed explanation will be omitted. In photometry,two-dimensional photometric processing can be done using an area sensor.Therefore, for example, the photometric areas for the main subject maybe set arbitrarily in a two-dimensional space (or two-dimensionally).The photometric points may be designed to be compatible withmulti-points, if necessary.

As described above, with the seventh embodiment, the photometric section81 becomes unnecessary and the photometric section anddistance-measuring section share the light-receiving element (areasensor), which makes it possible to provide an integral photometricdistance-measuring unit. Sharing the light-receiving element eliminatesparallax in the photometric visual field and distance-measuring visualfield. Therefore, the seventh embodiment has a spatial merit and enablesa higher-accuracy backlight decision to be made than a conventionalequivalent.

Explanation has been given using a camera capable of photometry anddistance measurement as an example. The subject matter of the presentinvention may be applied similarly to devices other than cameras. Theinvention, of course, may be applied similarly to a single device unit,such as a photometric distance-measuring unit.

Next, an eighth embodiment of the present invention will be explained.

FIG. 24 is a block diagram of a camera according to the eighthembodiment. First, the image of a subject (person) 143 is formed by aphotographic lens 135. The image-enters an imaging section 137 theimaging section 137 separates the image of the subject 143 into threekinds of color components (i.e., RGB components) and integrates them.The amounts of integration corresponding to the respective colorcomponents are outputted as subject image signals to an analog/digital(A/D) conversion section 137 a. The A/D conversion section 137 aconverts the inputted integration output into digital quantity andoutputs the digital signal to an image processing section 140 a.

The digital integration output (hereinafter, referred to as image data)inputted to the image processing section 140 a is subjected to tonecorrection at a tone correcting section 138. The tone correction isknown as a gamma (γ) conversion process. In the tone correction, the γvalue in the tone curve of the inputted data is corrected, therebymaking the brightness of the image proper. The tone correcting section138 emphasizes the dark part or the bright part, which makes natural thedistribution of brightness of the screen visible to our eyes inreproducing the image.

After the tone is corrected by the tone correcting section 138, the tonecorrecting section 138 supplies its output to an RGB signal/YC signal(RGB/YC) converting section 139. The RGB/YC converting section 139converts the image data inputted in the form of a RGB component signalinto a luminance (Y) signal and a color coordinate (C_(R), C_(B))signal. Of the signals converted into the YC components, the luminancesignal is outputted to a contour emphasizing section 140 and the colorcoordinate signal is outputted to an image compressing section 141.

The contour emphasizing section 140 carries out a contour emphasizingprocess of emphasizing the high contrast part of the inputted image(generally knows as a sharpness process). The contour emphasizingprocess will be explained later.

The image thus processed is inputted from the image processing section140 a to the image compressing section 141. The image compressingsection 141 compresses the inputted image using JPEG or the like andthen records the compressed image into a recording section 142.

As described above, the photographed image is recorded into therecording section 142 digitally. Such a series of image processes arecarried out by a computing section (CPU) 131 composed of a one-chipmicrocomputer or the like. The CPU 131 also performs photographingcontrol of the camera. The CPU 131 includes the functions of thebacklighting state judgment section and image processing section.

According to the signal from the CPU 131, the shutter section 137 bcontrols the charge accumulation time of the imaging section 137composed of CCD or the like. Before photographing, the CPU 131 focusesthe photographic lens 135 via a photographic lens driving (LD) section135 a. Focusing may be done on the basis of the subject distance dataobtained from the output of an A/D converting section 134.Alternatively, focusing may be done on the basis of the peak value ofthe contrast signal obtained from the image processing section 140 a.The image processing section 140 a produces the contrast signal bydisplacing the photographic lens 135 little by little.

The subject distance is calculated as follows. First, the images of thesubject 143 obtained via the two light-receiving lenses 132 a, 132 bprovided the base length (parallax) B apart are formed on the sensorarrays 133 a, 133 b. At this time, from the image position difference xof the image of the subject 143 based on the parallax of thelight-receiving lenses 132 a, 132 b, the CPU 131 calculates the subjectdistance according to the principle of trigonometrical distancemeasurements.

Use of the image (hereinafter, referred to as the image signal) of thesubject 143 formed on the sensor arrays 133 a, 133 b or the imagingsection 137 makes it possible to check if the subject 143 is dark oragainst light.

Specifically, the subject 143 often exists in the middle of the screenin terms of probability. In the case of FIG. 26A, since the image atleft is brighter than in the middle, it can be determined that thesubject is against light.

Furthermore, if the image data is low in luminance even after a specifictime of integration, or after the charge is accumulated, it can bedetermined that the subject has a low luminance. The higher theintensity of the incident light is, the larger photoelectric current thesensor arrays 133 a, 133 b and the imaging section 137 generate.Therefore, when the photoelectric current is integrated to a specificcapacity, the brighter the part, the larger the integration value, orthe darker the part, the smaller the integration value.

In FIG. 24, the distance-measuring unit is composed of thelight-receiving lenses 132 a, 132 b, sensor arrays 133 a, 133 b, and A/Dconverting section 134. The distance-measuring unit sets the subjectexisting at the point indicating the closest distance as the mainsubject and determines whether the subject is bright or dark on thebasis of the brightness of the point. That is, the distance-measuringunit determines whether the subject is against light, on the basis ofthe comparison with the integration values of the surroundings.

FIG. 25 shows the region monitored by both of the sensor arrays asregion 133 c and the region monitored by the imaging section 137 asregion 137 c. When the subject 143 is dark or against light, a strobelight emission circuit 136 a performs light emission control of a strobelight emission section 136, thereby supplementing the exposure of thesubject 143.

Next, FIG. 26A shows an example of the photographic scene supposed inthe eighth embodiment. When the person 143, the main subject, is againstlight, the luminance difference between the background and the personbecomes larger. At this time, in FIG. 26A, for example, when thebrightness in the x-direction with respect to the position of a specificcoordinate y0 in the vertical direction of the photographic screen ismonitored, the characteristic as shown in FIG. 26B is obtained. In theFIG. 26B, the position corresponding to the background is bright and theposition corresponding to the person 143 is dark. At this time, sincethe photographic scene of FIG. 26A is against light, the left half ofthe person 143 influenced by outdoor light is bright and the right halfof the person 143 inside the house is dark. In such a case, whenexposure is made so that the subject may lie within the permittedluminance range, there is a possibility that the contour of either thebackground or the person will disappear. In such a state, when theabove-described contour emphasizing process or γ conversion process iscarried out, an erroneous contour appears, noise occurs in the darkpart, or the bright part disappear in white, which results in anunnatural image.

This will be explained in more detail by reference to a histogram shownin FIG. 27A. In FIG. 27A, the abscissa axis indicates brightness(luminance) Bv and the ordinate axis indicates in frequency how manypixels of the brightness indicated by the abscissa axis there are. Sincein a backlighting scene, the difference in brightness between the brightpart and the dark part is large, the ratio of the number of pixelsoutputting bright data to the total number of pixels and the ratio ofthe number of pixels outputting dark data to the total number of pixelsare high, whereas the number of pixels outputting intermediate data issmall. As a result, a larger part of the image cannot be recognizedvisually. When the γ conversion process is performed on FIG. 27A so asto decrease the γ value, the result is as shown in FIG. 27B.

The γ conversion process at that time will be explained by reference toFIG. 29.

FIG. 29 shows how the brightness of the input and output images variesaccording to the γ value in the γ conversion process. Specifically, whenthe γ value becomes small (in the figure, γ=0.56), the dark part of theimage is emphasized, making it easier to see a change in the dark partof the image. The bright part of the image is corrected so that a changein the bright part may be weakened. On the other hand, when the γ valuebecomes large (in the figure, γ=1.8), the dark part of the image getsdarker, being painted over with black, and a change in the bright partof the image is emphasized.

Therefore, when FIG. 27A is subjected to the γ conversion process todecrease the γ value, the dark part in FIG. 27A is emphasized, with theresult that the emphasized part lies in the visually recognizable range.From the beginning, the dark part has a small signal quantity andtherefore the noise-to-signal ratio is relatively high. When the darkpart is emphasized in such a case, the noise component of the signal isemphasized, too. This impairs the discontinuity of gradation, renderingthe image undergone γ-conversion even worse.

In the eighth embodiment, to overcome this problem, the strobe lightemission section 136 is caused to emit light in the photographic sceneas shown in FIG. 26A, thereby obtaining an image as shown in FIG. 26C,that is, such an image as brings both the background and the mainsubject into the visually recognizable range, not an image against lightas shown in FIG. 28.

That is, when a luminance distribution with a large luminance differenceas shown in FIG. 26B or a histogram as shown in FIG. 27A has beenobtained from the sensor arrays 133 a, 133 b or the imaging section 137,strobe light is emitted and the light quantity at the main subject issupplemented as shown in FIG. 26D, thereby raising the luminancedistribution, which brings the background and the image of the personinto a specific latitude. In the histogram, the intermediate brightnessis increased with the supplementary light from the strobe unit as shownin FIG. 27C, which makes it possible to record the image with exposuresacrificing the dark part. In this case, it is not necessary toemphasize a specific brightness in the γ conversion process. Therefore,the contour emphasizing process is a normal one.

The contour emphasizing process will be explained in more detail byreference to FIGS. 30A and 30B. FIG. 30A shows the processes carried outin the contour emphasizing section 140 of FIG. 24 from a functionalviewpoint.

When the luminance signal data (input Y in FIG. 30A) 152 converted atthe RGB/YC converting section 139 is inputted to the contour emphasizingsection 140, a contour component extracting circuit 140A in the contouremphasizing section does Laplacian calculation of the inputted luminancesignal data 152 using a sharpening filter matrix 151 (FIG. 30B). As aresult, the image data whose central part is emphasized, or the contoursignal data 153, is created. The contour signal data 153 contained thenoise component of the luminance signal data 152, which has beenemphasized. Thus, the image will appear unnatural if the contouremphasis is performed by using the contour signal data 153 acquired forall pixels. Therefore, a limiting circuit 140B prevents the result ofcalculations lower than a specific contrast, or less than ΔY in thefigure from being inputted to an adder circuit 140C.

On-the other hand, the luminance signal data 152 is also inputted to theadder circuit 140C, with the result that the combination of theluminance signal date 152 and the contour signal data 153 becomes thefinal output Y′ of the contour emphasizing section 140.

By changing the invariables in the sharpening filter matrix, the degreeof contour emphasis can be changed. In addition, the degree of contouremphasis is also changed by changing ΔY in the limiting circuit 140B. Inthis case, making ΔY larger causes contour emphasis to be decreased,whereas making ΔY smaller causes contour emphasis to be increased.

Since there is a limit to the guide number showing the relationshipbetween the strobe light reaching distance and the stop of the camera,when the subject distance is too far, the main subject cannot be broughtinto a sufficient brightness, no matter how strong the strobe light is.As a result, an image as shown in FIG. 26E appears.

As described above, when the strobe light does not reach the mainsubject, exposure is made so as to bring only the bright part intolatitude 1 of FIG. 26F, with the result that the face of the person 143becomes pitch-dark at the cost of the background photographed properlyas shown in FIG. 26E. Thus, in such a scene, exposure is made on theoverexposure side, that is, in latitude 2 of FIG. 26F, which permits theface of the person 143 to be photographed properly. Then, in the γconversion process, the γ value is made larger to emphasize the brightpart, or a change in the luminance of the background, so that the imageof the background may not collapse. At this time, since the largeluminance difference still remains, contour emphasis would make theimage unnatural. Therefore, contour emphasis is caused to weaken.

Referring to a flowchart shown in FIG. 31, the sequence of photographingcontrol performed by the CPU 131 based on the aforementioned idea willbe explained.

First, when photographing control is started, distance measurement tocalculate the subject distance is made to determine a photographic scenein photographing (step S131). Next, on the basis of the calculatedsubject distance, the LD section 135 a is controlled to focus thephotographic lens 135 (step S132). In addition, photometry is performedto detect the brightness at the photographic screen and the distributionof brightness (step S133). Next, on the basis of the obtained data, itis determined whether the photographic scene is against light (stepS134).

Specifically, if the image data about the main subject 143 formed on thesensor arrays 133 a, 133 b or imaging section 137 is much smaller thanthe image data about the background, it is determined that thephotographic scene is against light. The method of detecting the mainsubject may be a method of detecting the distance distribution on thescreen with the distance-measuring unit as described above anddetermining the thing indicating the closest distance to be the mainsubject. Alternatively, a known method may be used. This method is todetect the contour of the subject from the data generated by the imagingsection 137. If the shape represents a man, the subject is determined tobe the main subject.

If it has been determined in step S134 that the photographic scene isagainst light, the light emission flag of the strobe unit is set high(step S135). Then, from the subject distance obtained in step S131, thestrobe light emission quantity GNo is calculated by a known flashmaticmethod (step S136). Next, when the strobe light emission section 136 hasbeen caused to emit light, it is determined whether strobe light reachesthe subject, that is, whether the subject distance obtained in step S131is closer than the strobe light reaching distance (step S137).

If it has been determined in step S137 that strobe light reaches thesubject (YES), it is determined from the background image data whetherthe exposure of the background exceeds a specific value (step S138).

In step S138, it is determined whether exposure is made so that thebackground can be visually recognized. That is, it is determined whetherexposure is brought to such overexposure that the background cannot bevisually recognized. More specifically, the determination is made on thebasis of whether the amount of exposure of the background exceeds theupper limit of the latitude of the imaging section 137. Therefore, ifthe latitude of the imaging section 137 is ±2EV, the specific amount is+2EV. Then, it is determined whether exposure of the background exceeds+2EV. In step S138, if it has been determined that exposure of thebackground exceeds the specific value (YES), setting is done in the γconversion process so that the γ value is increased (step S139) andcontour emphasis is weakened (step S140) and then control proceeds tostep S153. Making the γ value larger prevents the background image fromdisappearing in white as described earlier. Since the background lightcan be blurred with the contour of the main subject, correction toweaken contour emphasis is made at the same time. On the other hand, instep S138, if it has been determined that exposure of the backgrounddoes not exceed the specific amount (NO), setting is done so thatcorrection is made with the normal γ value, that is, γ=1 (step S141) andthen control goes to step S153. In this case, it is not necessary tochange the setting of contour emphasis, because the brightness of thebackground image is balanced with that of the main subject.

In step S137, if it has been determined that strobe light does not reachthe main subject (NO), it is determined whether the underexposure of themain subject is equal to or less than −2EV under the irradiation ofstrobe light (step S142). In step S142, it is determined whetherexposure is made so that the main subject can be visually recognized.That is, it is determined whether exposure is brought to suchunderexposure that the main subject cannot be visually recognized. Thethreshold of the determination is not limited to −2EV and may be set sothat it can be determined whether exposure is made so as to enable themain subject to be visually recognized. More specifically, the thresholdcan be determined on the basis of whether the amount of exposure of themain subject drops below the lower limit of the latitude of the imagingsection 137. In the eighth embodiment, let the latitude of the imagingsection 137 be ±2EV. Thus, in step S142, it is determined whether theunderexposure of the main subject is equal to or less then −2EV. In stepS142, if it has been determined that the underexposure is not equal toor less than −2EV, setting is done so as to make an exposure correctionof +1EV (step S143), because the illumination of the main subject bystrobe light is regarded as making almost no contribution to exposure.As a result, the dark part is made brighter.

This makes it possible to cause the amount of exposure of the mainsubject to lie within the latitude of the imaging section 137. Theamount of corrected exposure is not restricted to +1EV and may bedetermined so that, for example, the amount of exposure of the mainsubject may lie within the latitude of the imaging section 137. Whenexposure is corrected excessively, the high luminance part, such as thebackground, is overexposed. Therefore, the amount of corrected exposuremay be determined so that the amount of exposure of the main subject andthat of the background may lie within the latitude of the imagingsection 137 according to the difference in the amount of exposurebetween the main subject and the background. Thereafter, setting is doneso that the γ value may be increased (step S144) and contour emphasismay be decreased (step S145) and then control goes to step S153. On theother hand, in step S142, if it has been determined that the degree ofthe underexposure is equal to or less than −2EV, setting is done so thatthe γ value may be increased (step S146) and contour emphasis may bedecreased (step S147) and then control goes to step S153.

In step S134, if it has been determined that the photographic scene isnot against light, it is determined from the photometric value that thestrobe light emission section 136 is caused to emit light (step S148).If it has been determined that the strobe light emission section 136 iscaused to emit light (YES), the light emission flag of the strobe unitis set high (step S149). Thereafter, setting is done so that the γ valuemay be decreased (step S150) and contour emphasis may be decreased (stepS151) and then control goes to step S153. At this time, the γ value ismade smaller and the dark part is made as bright as possible. In thiscase, however, since the hair of the person 143 often cannot bedistinguished from the dark background as shown in FIG. 32, correctionto weaken contour emphasis is made.

On the other hand, in step S148, if it has been determined that thestrobe light emission section 136 is not caused to emit light (NO),setting is done so that a γ correction may be made with a normal γ value(step S152) and then control proceeds to step S153.

After the above operation, it is determined whether the light emissionflag of the strobe unit is high (step S153). If it has been determinedthat the light emission flag of the strobe unit is high (YES), it isdetermined whether setting has been done to make an exposure correction(step S154). If it has been determined that setting has been done tomake an exposure correction (YES), strobe photographing with an exposurecorrection is done (step S155) and then control goes to step S158. Instep S153, if it has been determined that the light emission flag of thestrobe unit is not high (NO), normal photographing without the lightemission of the strobe light emission section 136 is done (step S156).Thereafter, control goes to step S158. In step S154, if it has beendetermined that setting has not been done so that an exposure correctionmay be made (NO), strobe photographing without an exposure correction isdone (step S157) and then control proceeds to step S158.

After the image has been photographed by the above-described operations,the image processes, including the γ conversion process and contouremphasizing process, are carried out according to the aforementionedsettings (step S158) and the photographed image is recorded into therecording section 142 (step S159). After the photographed image isrecorded into the recording section 142, the photographing controlsequence is completed.

As described above, with the eighth embodiment, light is supplemented bythe strobe unit according to the state of the photographic scene (suchas backlighting) and a proper exposure correction and image processingare selected automatically, thereby performing photographing control.Therefore, proper photographing can be done even in a photographic sceneagainst light which would be difficult to reproduce in the prior art.Furthermore, since the photographer need not operate to make thecorrection, a camera excellent in snapshot capabilities can be provided.

Next, a ninth embodiment of the present invention will be explained byreference to FIG. 33.

In the ninth embodiment, instead of using a distance-measuring unit, orthe sensor arrays 133 a, 133 b, and the like, the imaging sectionprovided on the digital camera or the like, or the imaging section 137of FIG. 24, is used to measure a distance. The CPU 131 in the ninthembodiment includes the functions of an illumination state judgmentsection and a control section. Since the remaining configuration andoperation are the same as those in the eighth embodiment, explanation ofthem will be omitted.

FIG. 33 is a flowchart to help explain operation control beforephotographing is done with a camera according to the ninth embodiment.The operations subsequent to the flowchart are almost the same as thoseafter step S134 in FIG. 31.

First, the CPU 131 takes in an image with the imaging section 137 (stepS161). Then, the contrast of the taken-in image is detected (step S162).Next, it is determined whether the detected contrast is the peak of thecontrast (step S163). If it has been determined that it is not the peakof the contrast (NO), the photographic lens 135 is driven minutely (stepS167) and then control returns to step S161. These operations arerepeated until the peak of the contrast has been detected.

On the other hand, if it has been determined in step S163 that the peakof the contrast has been detected (YES), it is determined from thebrightness of the image whether the emission of strobe light isnecessary (step S164). If it has been determined that the emission ofstrobe light is not necessary (NO), control exits the flowchart andproceeds to step S134 in FIG. 31. In subsequent processes, photographingis done without the light emission of the strobe light emission section136.

In step S164, it has been determined that the emission of strobe lightis necessary (YES), a pre-emission of a small quantity of light iscarried out and the image at this time is taken in by the imagingsection 137 (step S165). Comparing the image with the image taken in atstep S161 enables the contribution rate of strobe light duringphotographing. From this, information as to whether strobe light reachesthe subject during photographing or whether the exposure state by theirradiation of strobe light is in underexposure is estimated and thenthe proper amount of emission of strobe light is calculated (step S166).After the amount of emission of strobe light is calculated, controlexits the flowchart and goes to step S134 in FIG. 31.

For example, in step S161, if the amount of integration as shown in FIG.34A, or the image data, is obtained, and the image data as shown in FIG.34B or FIG. 34C is obtained with the pre-emission of light in step S164,the difference (indicated by STUP in the figure) between FIGS. 34A and34B or FIGS. 34A and 34C indicates the rate of the contribution ofstrobe light.

After the pre-emission of light, when the image data in FIG. 34B isobtained, the central part, or the main subject, is less bright than thebackground. Therefore, since the strobe light is regarded as making nocontribution, step S138 in FIG. 31 is branched to step S139. On theother hand, after the pre-emission of light, when the image data in FIG.34C is obtained, the brightness of the background and that of the mainsubject are almost at the same level, so that step S138 in FIG. 31 isbranched to step S141.

As explained above, with the ninth embodiment, suitable photographingcontrol is performed according to the photographic scene with theimaging section of the digital camera without using a specialdistance-measuring unit. This makes it possible to photograph abacklighting scene which was difficult to reproduce in the prior art,without using a special distance-measuring unit.

Next, referring to FIGS. 35 to 38, a tenth embodiment of the presentinvention will be explained. The configuration of the tenth embodimentis achieved by applying an equivalent configuration to that of theeighth or ninth embodiment.

In the tenth embodiment, when the photographic scene is against lightand strobe light emission control is performed, control is performed sothat the background and a person, the main subject, may have a properbrightness. This will be explained by reference to FIGS. 36A and 36B.FIG. 36A shows a change in the amount of integration of the backgroundsubject with respect to time after the emission of strobe light. At thistime, the strobe light does not reach the background subject. Since thephotographic scene is against light from the beginning, the backgroundsubject is exposed at the proper level for the proper exposure time evenunder only steady light components, such as natural light.

FIG. 36B shows a change in the amount of integration of the main subjectwith respect to time after the emission of strobe light. At this time,the steady light components of the main subject are supplemented withstrobe light, which enables exposure to be made at the proper level forthe proper exposure time.

There is a limit to the amount of emission of strobe light. Therefore,only with steady light, such as natural light, it is possible that themain subject has not yet been exposed at the proper level, even when thebackground has been exposed at the proper level for the proper exposuretime as shown in FIGS. 37A and 37B. In FIG. 37B, the difference betweenthe amount of integration of the main subject and that of the backgroundsubject (at the proper exposure level) is represented as the amount ofunderexposure in FIG. 37B. The amount of underexposure can be estimatedon the basis of the result of photometry and the result of distancemeasurement before photographing and the limit of guide number of thestrobe unit.

FIGS. 38A and 38C show examples of a change in the brightness from theposition of the main subject to the position of the background. Asdescribed above, when the photographic scene is underexposed, thebrightness difference ΔBV between the person, the main subject, and thebackground subject varies with the degree of underexposure. If the ΔBVis small, that is, if the photographic scene is as shown in FIG. 38A,the person and the background cannot be separated distinctly unless theminute change in the light quantity is emphasized. For this reason,correction is made by a γ conversion process with the characteristic asshown in FIG. 38B. In addition, contour emphasis may be made.

On the other hand, when a balance in brightness between the backgroundand the person is clearly bad, a γ conversion process with thecharacteristic as shown in FIG. 38D is carried out, because compressingthe changed part to emphasize the bright part improves a balance betweenthe background and the person.

FIG. 35 shows a flowchart for photographing control in backlightingincluding switching control of the γ conversion process. In theflowchart, explanation will be given, provided that the photographicscene is against light. Explanation of the process of making a decisionon backlighting will be omitted.

First, the CPU 131 takes in an image with the imaging section 137 (stepS171). Then, the photographic lens 135 is focused (step S172). Thefocusing may be done by the method of either the 8th or 9th embodiment.In the tenth embodiment, the method of the second embodiment is used.

Next, the strobe light emission section 136 is caused to emit lightpreviously and the imaging section 137 takes in the image at that time(step S173). Next, the exposure time that brings the background subjectto the proper exposure level is calculated (step S174). Thereafter, theamount of emission of light by the strobe unit necessary to bring themain subject to the proper exposure level is determined (step S175).Then, the brightness difference ΔBV between the main subject and thebackground subject is found (step S176).

Next, it is determined whether ΔBV is larger than a specific level (stepS177). If ΔBV is equal to or less than the specific level, that is, ifthe photographic scene is as shown in FIG. 38A, setting is done so as tocarry out a γ conversion process with the characteristic of FIG. 38C toemphasize a change in ΔBV (step S178). Then, after setting is done so asto emphasize the contour near ΔBV (step S179), control proceeds to stepS183.

On the other hand, if it has been determined in step S177 that ΔBV islarger than the specific level, that is, the photographic scene is asshown in FIG. 38C, setting is done so as to carry out a γ conversionprocess with the characteristic of FIG. 38D to weaken (compress) achange in ΔBV (step S180) Furthermore, setting is done so as to weakenthe contour near ΔBV (step S181). In this case, the bright part of thebackground can disappear in white. Therefore, after setting is done toemphasize the contour of the bright part (step S182), control goes tostep S183.

After such operations, strobe photographing is done (step S183). Then,after the image is processed according to the above settings (stepS184), the resulting image is recorded into the recording section 142(step S185). After the image is recorded in the recording section 142,the backlight photographing control in the flowchart is completed.

As described above, with the tenth embodiment, the image processing iseffected automatically on the basis of the difference in brightnessbetween the background and the main subject during backlighting. Thismakes it possible to take a picture with a good balance in tone betweenthe background and the subject.

Accordingly, with the present invention, it is possible to provide acamera which is capable of producing a natural image according to thephotographic scene and excels in snapshot capabilities. The presentinvention is not limited to the above embodiments and may be practicedor embodied in still other ways without departing from the spirit oressential character thereof.

1. A camera comprising: a sensor array which detects an image signal ofa subject existing in a specific position on a photographic screen andwhich includes a plurality of sensors; a computing section whichcalculates an average value of outputs of a part of said plurality ofsensors in the sensor array; an average photometric sensor which detectsan average brightness at the photographic screen; an average luminancecomputing section which calculates an average luminance value at thephotographic screen based on an output of the average photometricsensor; a subject state judgment section which determines a state of thesubject by comparing the average value of the sensor outputs with theaverage luminance value; an optical sensor which detects a luminancevalue of an average brightness at a wavelength area different from aphotometric wavelength area detected by the average photometric sensorat the photographic screen; a subject field state judgment section whichdetermines a state of a subject field including the subject by comparingthe average luminance value with the luminance value detected by theoptical sensor; and an exposure control determining section whichdetermines exposure control during photographing based on the averageluminance value and results of determinations of the subject statejudgment section and the subject field state judgment section.
 2. Thecamera according to claim 1, further comprising: a photographic opticalsystem capable of variable power; a first optical system which directslight from the subject to the sensor array and is different from thephotographic optical system; and a second optical system which directsthe light from the subject to the average photometric sensor and isdifferent from the photographic optical system, wherein the averagephotometric sensor includes a plurality of light-receiving portions,each having a different light-receiving range, and changes a sizeoccupied by the part of said plurality of sensors in the sensor arrayused in the computing section but also tire a light-receiving range ofthe average photometric sensor according to a variable power state ofthe photographic optical system.
 3. The camera according to claim 1,wherein the sensor array produces a distance measuring image signal, andwherein the outputs of the part of said plurality of sensors in thesensor array used in the computing section correspond to the sensoroutputs used for distance measurement.
 4. The camera according to claim3, further comprising a photographic optical system; wherein the sensorarray is adapted to form a distance-measuring image signal at aplurality of positions on the photographic screen, and wherein theoutputs of the part of said plurality of sensors in the sensor arrayused in the computing section correspond to the outputs of the sensorsused to output distance data used to focus the photographic opticalsystem among a plurality of positions on the photographic screen.
 5. Thecamera according to claim 1, further comprising: a strobe unit whichemits strobe light toward the subject; and a judgment section whichdetermines whether the strobe light reaches the subject, wherein theexposure control determining section determines exposure control duringphotographing, taking into account a result of a determination of thejudgment section.
 6. The camera according to claim 5, wherein theexposure control determining section determines exposure control duringphotographing so as to cause the strobe unit to emit light and performexposure control, when the judgment section has determined that thestrobe light reaches the subject and the result of the determination ofthe subject state judgment section has shown a specific state.
 7. Thecamera according to claim 6, wherein: the subject state judgment sectiondetermines whether the subject is against light, and the specific stateis a state where the subject is against light.
 8. The camera accordingto claim 5, further comprising a discriminative section whichdiscriminates a mode of the camera, wherein the exposure controldetermining section determines exposure control during photographing,taking into account a result of discrimination of the discriminativesection.
 9. A camera comprising: a sensor array which detects an imagesignal of a subject existing in a specific position on a photographicscreen and which includes a plurality of sensors; a computing sectionwhich calculates an average value of outputs of a part of said pluralityof sensors in the sensor array; an average photometric sensor whichdetects an average brightness of visible light at the photographicscreen; an average luminance computing section which calculates anaverage luminance value at the photographic screen based on an output ofthe average photometric sensor; an infrared sensor which detects aninfrared luminance value indicating a brightness of average infraredlight at the photographic screen; a subject state judgment section whichdetermines a state of the subject by comparing the average value of thesensor outputs with the average luminance value; a subject field statejudgment section which determines a state of a subject field includingthe subject by comparing the average luminance value with the infraredluminance value; and an exposure control determining section whichdetermines exposure control during photographing based on the averageluminance value and results of determinations of the subject statejudgment section and the subject field state judgment section.
 10. Thecamera according to claim 9, further comprising: a strobe unit whichemits strobe light toward the subject; and a judgment section whichdetermine whether the strobe light reaches the subject, wherein theexposure control determining section determines (i) exposure controlduring photographing so as to cause the strobe unit to emit light andperform exposure control, when the judgment section determines that thestrobe light reaches the subject and the result of the determination atthe subject state judgment section has shown a specific state, and (ii)determines exposure control during photographing so as to cause thestrobe unit to emit light and perform exposure control, when thejudgment section determines that the strobe light reaches the subjectand the result of the determination at the subject field state judgmentsection has shown a specific state.
 11. The camera according to claim10, wherein: the subject state judgment section determines whether thesubject is against light, and the specific state is a state where thesubject is against light.
 12. The camera according to claim 10, wherein:the subject field state judgment section determines whether the lightsource of the subject field is artificial, and the specific state is astate where the light source of the subject field is artificial.
 13. Thecamera according to claim 10, further comprising a discriminativesection which discriminates a mode of the camera, wherein the subjectstate judgment section does not make a decision when the discriminativesection has determined that the camera is in a specific mode.
 14. Thecamera according to claim 13, wherein the specific mode is at least oneof a strobe OFF mode, a spot photometric mode, and an infinitephotographic mode.
 15. The camera according to claim 10, furthercomprising a discriminative section which discriminates a mode of thecamera, wherein the subject field state judgment section does not make adecision when the discriminative section has determined that the camerais in a specific mode.
 16. The camera according to claim 15, wherein thespecific mode is at least one of a strobe OFF mode, a spot photometricmode, and an infinite photographic mode.
 17. The camera according toclaim 9, further comprising: a photographic optical system; and a finderwhich is provided separately from the photographic optical system forviewing an image of the subject, wherein the sensor array and theaverage photometric sensor are provided near the finder.
 18. The cameraaccording to claim 17, wherein the infrared sensor is provided fartheraway from the finder than from the average photometric sensor and sensorarray.
 19. The camera according to claim 1, wherein the optical sensoris adapted to receive a signal from a remote control unit to operate thecamera by remote control.
 20. The camera according to claim 9, whereinthe sensor array generates a distance measuring image signal and theinfrared sensor is adapted to receive the signal from the remote controlunit to operate the camera by remote control.